Remove checks for features available in C++17

This patch removes most of the checks that are made using C++20
__cpp_* macros for features available in C++17 and earlier.
Library feature check macros (__cpp_lib_*) are unaffected.

Change-Id: I557b2bd0d4ff09b13837555e9880eb28e0355f64
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

17 files changed, 2 insertions, 78 deletions

diff --git a/src/concurrent/qtconcurrentfunctionwrappers.h b/src/concurrent/qtconcurrentfunctionwrappers.h
index 1c882d3f19..08966115d6 100644
--- a/src/concurrent/qtconcurrentfunctionwrappers.h
+++ b/src/concurrent/qtconcurrentfunctionwrappers.h
@@ -129,7 +129,6 @@ struct ReduceResultType<R(*)(A...)>
     using ResultType = typename std::tuple_element<0, std::tuple<A...>>::type;
 };
 
-#if defined(__cpp_noexcept_function_type) && __cpp_noexcept_function_type >= 201510
 template <class U, class V>
 struct ReduceResultType<void(*)(U&,V) noexcept>
 {
@@ -141,7 +140,6 @@ struct ReduceResultType<T(C::*)(U) noexcept>
 {
     using ResultType = C;
 };
-#endif
 
 template<class T, class Enable = void>
 struct hasCallOperator : std::false_type
diff --git a/src/corelib/global/qcompilerdetection.h b/src/corelib/global/qcompilerdetection.h
index 273575c31f..bfa4f89105 100644
--- a/src/corelib/global/qcompilerdetection.h
+++ b/src/corelib/global/qcompilerdetection.h
@@ -1114,10 +1114,8 @@
 #  define Q_DECL_DEPRECATED_X(x) [[deprecated(x)]]
 #endif
 
-#if defined(__cpp_enumerator_attributes) && __cpp_enumerator_attributes >= 201411
-#  define Q_DECL_ENUMERATOR_DEPRECATED Q_DECL_DEPRECATED
-#  define Q_DECL_ENUMERATOR_DEPRECATED_X(x) Q_DECL_DEPRECATED_X(x)
-#endif
+#define Q_DECL_ENUMERATOR_DEPRECATED Q_DECL_DEPRECATED
+#define Q_DECL_ENUMERATOR_DEPRECATED_X(x) Q_DECL_DEPRECATED_X(x)
 
 /*
  * Fallback macros to certain compiler features
@@ -1153,12 +1151,6 @@
 #ifndef Q_DECL_DEPRECATED_X
 #  define Q_DECL_DEPRECATED_X(text) Q_DECL_DEPRECATED
 #endif
-#ifndef Q_DECL_ENUMERATOR_DEPRECATED
-#  define Q_DECL_ENUMERATOR_DEPRECATED
-#endif
-#ifndef Q_DECL_ENUMERATOR_DEPRECATED_X
-#  define Q_DECL_ENUMERATOR_DEPRECATED_X(x)
-#endif
 #ifndef Q_DECL_EXPORT
 #  define Q_DECL_EXPORT
 #endif
diff --git a/src/corelib/kernel/qobjectdefs_impl.h b/src/corelib/kernel/qobjectdefs_impl.h
index c35d9aa7a7..a3068e1712 100644
--- a/src/corelib/kernel/qobjectdefs_impl.h
+++ b/src/corelib/kernel/qobjectdefs_impl.h
@@ -158,7 +158,6 @@ namespace QtPrivate {
             (o->*f)((*reinterpret_cast<typename RemoveRef<SignalArgs>::Type *>(arg[II+1]))...), ApplyReturnValue<R>(arg[0]);
         }
     };
-#if defined(__cpp_noexcept_function_type) && __cpp_noexcept_function_type >= 201510
     template <int... II, typename... SignalArgs, typename R, typename... SlotArgs, typename SlotRet, class Obj>
     struct FunctorCall<IndexesList<II...>, List<SignalArgs...>, R, SlotRet (Obj::*)(SlotArgs...) noexcept> {
         static void call(SlotRet (Obj::*f)(SlotArgs...) noexcept, Obj *o, void **arg) {
@@ -171,7 +170,6 @@ namespace QtPrivate {
             (o->*f)((*reinterpret_cast<typename RemoveRef<SignalArgs>::Type *>(arg[II+1]))...), ApplyReturnValue<R>(arg[0]);
         }
     };
-#endif
 
     template<class Obj, typename Ret, typename... Args> struct FunctionPointer<Ret (Obj::*) (Args...)>
     {
@@ -210,7 +208,6 @@ namespace QtPrivate {
         }
     };
 
-#if defined(__cpp_noexcept_function_type) && __cpp_noexcept_function_type >= 201510
     template<class Obj, typename Ret, typename... Args> struct FunctionPointer<Ret (Obj::*) (Args...) noexcept>
     {
         typedef Obj Object;
@@ -247,7 +244,6 @@ namespace QtPrivate {
             FunctorCall<typename Indexes<ArgumentCount>::Value, SignalArgs, R, Function>::call(f, arg);
         }
     };
-#endif
 
     template<typename Function, int N> struct Functor
     {
diff --git a/src/corelib/thread/qlocking_p.h b/src/corelib/thread/qlocking_p.h
index 9a796cf7f7..5fb80454df 100644
--- a/src/corelib/thread/qlocking_p.h
+++ b/src/corelib/thread/qlocking_p.h
@@ -84,15 +84,11 @@ QT_BEGIN_NAMESPACE
 namespace {
 
 template <typename Mutex, typename Lock =
-#if defined(__cpp_guaranteed_copy_elision) && __cpp_guaranteed_copy_elision >= 201606L
 # if defined(__cpp_lib_scoped_lock) && __cpp_lib_scoped_lock >= 201703L
           std::scoped_lock
 # else
           std::lock_guard
 # endif
-#else
-          std::unique_lock
-#endif
           <typename std::decay<Mutex>::type>
 >
 Lock qt_scoped_lock(Mutex &mutex)
diff --git a/src/corelib/tools/qlist.h b/src/corelib/tools/qlist.h
index 0329dd37da..07e5970faf 100644
--- a/src/corelib/tools/qlist.h
+++ b/src/corelib/tools/qlist.h
@@ -663,12 +663,10 @@ public:
     }
 };
 
-#if defined(__cpp_deduction_guides) && __cpp_deduction_guides >= 201606
 template <typename InputIterator,
           typename ValueType = typename std::iterator_traits<InputIterator>::value_type,
           QtPrivate::IfIsInputIterator<InputIterator> = true>
 QList(InputIterator, InputIterator) -> QList<ValueType>;
-#endif
 
 template <typename T>
 inline void QList<T>::resize_internal(qsizetype newSize)
diff --git a/src/corelib/tools/qscopeguard.h b/src/corelib/tools/qscopeguard.h
index 8270f41a2e..cc9e8db209 100644
--- a/src/corelib/tools/qscopeguard.h
+++ b/src/corelib/tools/qscopeguard.h
@@ -86,9 +86,7 @@ private:
     bool m_invoke = true;
 };
 
-#ifdef __cpp_deduction_guides
 template <typename F> QScopeGuard(F(&)()) -> QScopeGuard<F(*)()>;
-#endif
 
 //! [qScopeGuard]
 template <typename F>
diff --git a/src/corelib/tools/qset.h b/src/corelib/tools/qset.h
index 565b8b5691..9aecbff5bc 100644
--- a/src/corelib/tools/qset.h
+++ b/src/corelib/tools/qset.h
@@ -235,12 +235,10 @@ private:
     Hash q_hash;
 };
 
-#if defined(__cpp_deduction_guides) && __cpp_deduction_guides >= 201606
 template <typename InputIterator,
           typename ValueType = typename std::iterator_traits<InputIterator>::value_type,
           QtPrivate::IfIsInputIterator<InputIterator> = true>
 QSet(InputIterator, InputIterator) -> QSet<ValueType>;
-#endif
 
 template <typename T>
 size_t qHash(const QSet<T> &key, size_t seed = 0)
diff --git a/src/corelib/tools/qvarlengtharray.h b/src/corelib/tools/qvarlengtharray.h
index 3aa5e70114..90be3b3299 100644
--- a/src/corelib/tools/qvarlengtharray.h
+++ b/src/corelib/tools/qvarlengtharray.h
@@ -386,12 +386,10 @@ private:
     }
 };
 
-#if defined(__cpp_deduction_guides) && __cpp_deduction_guides >= 201606
 template <typename InputIterator,
           typename ValueType = typename std::iterator_traits<InputIterator>::value_type,
           QtPrivate::IfIsInputIterator<InputIterator> = true>
 QVarLengthArray(InputIterator, InputIterator) -> QVarLengthArray<ValueType>;
-#endif
 
 template <class T, qsizetype Prealloc>
 Q_INLINE_TEMPLATE QVarLengthArray<T, Prealloc>::QVarLengthArray(qsizetype asize)
diff --git a/src/gui/painting/qrgba64.h b/src/gui/painting/qrgba64.h
index 2c644c4cf0..e326c03bfc 100644
--- a/src/gui/painting/qrgba64.h
+++ b/src/gui/painting/qrgba64.h
@@ -118,7 +118,6 @@ public:
     constexpr quint8 alpha8() const { return div_257(alpha()); }
     constexpr uint toArgb32() const
     {
-#if defined(__cpp_constexpr) && __cpp_constexpr-0 >= 201304
         quint64 br = rgba & Q_UINT64_C(0xffff0000ffff);
         quint64 ag = (rgba >> 16) & Q_UINT64_C(0xffff0000ffff);
         br += Q_UINT64_C(0x8000000080);
@@ -136,9 +135,6 @@ public:
              | (ag         & 0xff00)
              | ((br >> 32) & 0xff);
 #endif
-#else
-        return uint((alpha8() << 24) | (red8() << 16) | (green8() << 8) | blue8());
-#endif
     }
     constexpr ushort toRgb16() const
     {
diff --git a/tests/auto/corelib/global/qglobal/tst_qglobal.cpp b/tests/auto/corelib/global/qglobal/tst_qglobal.cpp
index a5bf9cf34f..7323cfe545 100644
--- a/tests/auto/corelib/global/qglobal/tst_qglobal.cpp
+++ b/tests/auto/corelib/global/qglobal/tst_qglobal.cpp
@@ -535,8 +535,6 @@ void tst_QGlobal::testqOverload()
     QVERIFY(QConstOverload<QByteArray>::of(&Overloaded::mixedFoo) ==
              static_cast<void (Overloaded::*)(QByteArray) const>(&Overloaded::mixedFoo));
 
-#if defined(__cpp_variable_templates) && __cpp_variable_templates >= 201304 // C++14
-
     // void returning free overloaded functions
     QVERIFY(qOverload<>(&freeOverloaded) ==
              static_cast<void (*)()>(&freeOverloaded));
@@ -580,7 +578,6 @@ void tst_QGlobal::testqOverload()
 
     QVERIFY(qConstOverload<QByteArray>(&Overloaded::mixedFoo) ==
              static_cast<void (Overloaded::*)(QByteArray) const>(&Overloaded::mixedFoo));
-#endif
 
 #endif
 }
diff --git a/tests/auto/corelib/kernel/qmetaobject/tst_qmetaobject.cpp b/tests/auto/corelib/kernel/qmetaobject/tst_qmetaobject.cpp
index 968ccee043..f13ffe8354 100644
--- a/tests/auto/corelib/kernel/qmetaobject/tst_qmetaobject.cpp
+++ b/tests/auto/corelib/kernel/qmetaobject/tst_qmetaobject.cpp
@@ -827,7 +827,6 @@ void tst_QMetaObject::invokePointer()
         QCOMPARE(obj.slotResult, QString("sl1:bubu"));
     }
     QCOMPARE(countedStructObjectsCount, 0);
-#ifdef __cpp_init_captures
     {
         CountedStruct str;
         std::unique_ptr<int> ptr( new int );
@@ -835,7 +834,6 @@ void tst_QMetaObject::invokePointer()
         QCOMPARE(obj.slotResult, QString("sl1:1"));
     }
     QCOMPARE(countedStructObjectsCount, 0);
-#endif
 }
 
 void tst_QMetaObject::invokeQueuedMetaMember()
@@ -1151,7 +1149,6 @@ void tst_QMetaObject::invokeBlockingQueuedPointer()
         QCOMPARE(exp, QString("yessir"));
         QCOMPARE(obj.slotResult, QString("sl1:bubu"));
     }
-#ifdef __cpp_init_captures
     {
         std::unique_ptr<int> ptr(new int);
         QVERIFY(QMetaObject::invokeMethod(&obj,
@@ -1159,7 +1156,6 @@ void tst_QMetaObject::invokeBlockingQueuedPointer()
                                           Qt::BlockingQueuedConnection));
         QCOMPARE(obj.slotResult, QString("sl1:hehe"));
     }
-#endif
     QVERIFY(QMetaObject::invokeMethod(&obj, [&](){obj.moveToThread(QThread::currentThread());}, Qt::BlockingQueuedConnection));
     t.quit();
     QVERIFY(t.wait());
diff --git a/tests/auto/corelib/text/qstringapisymmetry/tst_qstringapisymmetry.cpp b/tests/auto/corelib/text/qstringapisymmetry/tst_qstringapisymmetry.cpp
index b42019bf04..543449c5e6 100644
--- a/tests/auto/corelib/text/qstringapisymmetry/tst_qstringapisymmetry.cpp
+++ b/tests/auto/corelib/text/qstringapisymmetry/tst_qstringapisymmetry.cpp
@@ -1509,7 +1509,6 @@ void tst_QStringApiSymmetry::tok_impl() const
         QCOMPARE(toQStringList(tok), resultCS);
     }
 
-#ifdef __cpp_deduction_guides
     QCOMPARE(toQStringList(QStringTokenizer{haystack, needle}), resultCS);
     QCOMPARE(toQStringList(QStringTokenizer{haystack, needle, Qt::KeepEmptyParts, Qt::CaseSensitive}), resultCS);
     QCOMPARE(toQStringList(QStringTokenizer{haystack, needle, Qt::CaseInsensitive, Qt::KeepEmptyParts}), resultCIS);
@@ -1522,7 +1521,6 @@ void tst_QStringApiSymmetry::tok_impl() const
         // yet `tok` should have kept a copy alive as needed:
         QCOMPARE(toQStringList(tok), resultCS);
     }
-#endif // __cpp_deduction_guides
 
     if constexpr (has_tokenize_method_v<Haystack>) {
         QCOMPARE(toQStringList(haystack.tokenize(needle)), resultCS);
diff --git a/tests/auto/corelib/text/qstringview/tst_qstringview.cpp b/tests/auto/corelib/text/qstringview/tst_qstringview.cpp
index a78004f04d..3d95022181 100644
--- a/tests/auto/corelib/text/qstringview/tst_qstringview.cpp
+++ b/tests/auto/corelib/text/qstringview/tst_qstringview.cpp
@@ -552,13 +552,11 @@ void tst_QStringView::tokenize() const
     QFETCH(const QStringList, result);
 
     // lvalue QString
-#ifdef __cpp_deduction_guides
     {
         auto rit = result.cbegin();
         for (auto sv : QStringTokenizer{str, sep})
             QCOMPARE(sv, *rit++);
     }
-#endif
     {
         auto rit = result.cbegin();
         for (auto sv : QStringView{str}.tokenize(sep))
@@ -566,13 +564,11 @@ void tst_QStringView::tokenize() const
     }
 
     // rvalue QString
-#ifdef __cpp_deduction_guides
     {
         auto rit = result.cbegin();
         for (auto sv : QStringTokenizer{str, QString{sep}})
             QCOMPARE(sv, *rit++);
     }
-#endif
     {
         auto rit = result.cbegin();
         for (auto sv : QStringView{str}.tokenize(QString{sep}))
@@ -580,13 +576,11 @@ void tst_QStringView::tokenize() const
     }
 
     // (rvalue) QChar
-#ifdef __cpp_deduction_guides
     if (sep.size() == 1) {
         auto rit = result.cbegin();
         for (auto sv : QStringTokenizer{str, sep.front()})
             QCOMPARE(sv, *rit++);
     }
-#endif
     if (sep.size() == 1) {
         auto rit = result.cbegin();
         for (auto sv : QStringView{str}.tokenize(sep.front()))
@@ -594,13 +588,11 @@ void tst_QStringView::tokenize() const
     }
 
     // (rvalue) char16_t
-#ifdef __cpp_deduction_guides
     if (sep.size() == 1) {
         auto rit = result.cbegin();
         for (auto sv : QStringTokenizer{str, *qToStringViewIgnoringNull(sep).utf16()})
             QCOMPARE(sv, *rit++);
     }
-#endif
     if (sep.size() == 1) {
         auto rit = result.cbegin();
         for (auto sv : QStringView{str}.tokenize(*qToStringViewIgnoringNull(sep).utf16()))
@@ -615,20 +607,17 @@ void tst_QStringView::tokenize() const
         return literal;
     };
     const std::unique_ptr<const char16_t[]> literal = make_literal(sep);
-#ifdef __cpp_deduction_guides
     {
         auto rit = result.cbegin();
         for (auto sv : QStringTokenizer{str, literal.get()})
             QCOMPARE(sv, *rit++);
     }
-#endif
     {
         auto rit = result.cbegin();
         for (auto sv : QStringView{str}.tokenize(literal.get()))
             QCOMPARE(sv, *rit++);
     }
 
-#ifdef __cpp_deduction_guides
 #ifdef __cpp_lib_ranges
     // lvalue QString
     {
@@ -657,7 +646,6 @@ void tst_QStringView::tokenize() const
         QCOMPARE(result, actual);
     }
 #endif // __cpp_lib_ranges
-#endif // __cpp_deduction_guides
 }
 
 template <typename Char>
diff --git a/tests/auto/corelib/tools/qlist/tst_qlist.cpp b/tests/auto/corelib/tools/qlist/tst_qlist.cpp
index 48931a81ea..3d26720fab 100644
--- a/tests/auto/corelib/tools/qlist/tst_qlist.cpp
+++ b/tests/auto/corelib/tools/qlist/tst_qlist.cpp
@@ -1143,7 +1143,6 @@ void tst_QList::count() const
 
 void tst_QList::cpp17ctad() const
 {
-#ifdef __cpp_deduction_guides
 #define QVERIFY_IS_VECTOR_OF(obj, Type) \
     QVERIFY2((std::is_same<decltype(obj), QList<Type>>::value), \
              QMetaType::fromType<decltype(obj)::value_type>().name())
@@ -1163,9 +1162,6 @@ void tst_QList::cpp17ctad() const
     CHECK(QString, QStringLiteral("one"), QStringLiteral("two"), QStringLiteral("three"));
 #undef QVERIFY_IS_VECTOR_OF
 #undef CHECK
-#else
-    QSKIP("This test requires C++17 Constructor Template Argument Deduction support enabled in the compiler.");
-#endif
 }
 
 void tst_QList::data() const
diff --git a/tests/auto/corelib/tools/qscopeguard/tst_qscopeguard.cpp b/tests/auto/corelib/tools/qscopeguard/tst_qscopeguard.cpp
index 21567137fd..90b3557ef5 100644
--- a/tests/auto/corelib/tools/qscopeguard/tst_qscopeguard.cpp
+++ b/tests/auto/corelib/tools/qscopeguard/tst_qscopeguard.cpp
@@ -94,7 +94,6 @@ static int s_globalState = 0;
 
 void tst_QScopeGuard::construction()
 {
-#ifdef __cpp_deduction_guides
     QScopeGuard fromLambda([] { });
     QScopeGuard fromFunction(func);
     QScopeGuard fromFunctionPointer(&func);
@@ -105,14 +104,10 @@ void tst_QScopeGuard::construction()
     std::function<void()> stdFunction(func);
     QScopeGuard fromNamedStdFunction(stdFunction);
 #endif
-#else
-    QSKIP("This test requires C++17 Class Template Argument Deduction support enabled in the compiler.");
-#endif
 }
 
 void tst_QScopeGuard::constructionFromLvalue()
 {
-#ifdef __cpp_deduction_guides
     Callable::resetCounts();
     {
         Callable callable;
@@ -127,14 +122,10 @@ void tst_QScopeGuard::constructionFromLvalue()
     }
     QCOMPARE(Callable::copied, 1);
     QCOMPARE(Callable::moved, 0);
-#else
-    QSKIP("This test requires C++17 Class Template Argument Deduction support enabled in the compiler.");
-#endif
 }
 
 void tst_QScopeGuard::constructionFromRvalue()
 {
-#ifdef __cpp_deduction_guides
     Callable::resetCounts();
     {
         Callable callable;
@@ -149,9 +140,6 @@ void tst_QScopeGuard::constructionFromRvalue()
     }
     QCOMPARE(Callable::copied, 0);
     QCOMPARE(Callable::moved, 1);
-#else
-    QSKIP("This test requires C++17 Class Template Argument Deduction support enabled in the compiler.");
-#endif
 }
 
 void tst_QScopeGuard::leavingScope()
diff --git a/tests/auto/corelib/tools/qset/tst_qset.cpp b/tests/auto/corelib/tools/qset/tst_qset.cpp
index 490e8e97fd..421657dc27 100644
--- a/tests/auto/corelib/tools/qset/tst_qset.cpp
+++ b/tests/auto/corelib/tools/qset/tst_qset.cpp
@@ -339,7 +339,6 @@ void tst_QSet::clear()
 
 void tst_QSet::cpp17ctad()
 {
-#ifdef __cpp_deduction_guides
 #define QVERIFY_IS_SET_OF(obj, Type) \
     QVERIFY2((std::is_same<decltype(obj), QSet<Type>>::value), \
              QMetaType::fromType<decltype(obj)::value_type>().name())
@@ -359,9 +358,6 @@ void tst_QSet::cpp17ctad()
     CHECK(QString, QStringLiteral("one"), QStringLiteral("two"), QStringLiteral("three"));
 #undef QVERIFY_IS_SET_OF
 #undef CHECK
-#else
-    QSKIP("This test requires C++17 Constructor Template Argument Deduction support enabled in the compiler.");
-#endif
 }
 
 void tst_QSet::remove()
diff --git a/tests/auto/corelib/tools/qvarlengtharray/tst_qvarlengtharray.cpp b/tests/auto/corelib/tools/qvarlengtharray/tst_qvarlengtharray.cpp
index 0598a39cb6..6e95577655 100644
--- a/tests/auto/corelib/tools/qvarlengtharray/tst_qvarlengtharray.cpp
+++ b/tests/auto/corelib/tools/qvarlengtharray/tst_qvarlengtharray.cpp
@@ -907,7 +907,6 @@ void tst_QVarLengthArray::count()
 
 void tst_QVarLengthArray::cpp17ctad()
 {
-#ifdef __cpp_deduction_guides
 #define QVERIFY_IS_VLA_OF(obj, Type) \
     QVERIFY2((std::is_same<decltype(obj), QVarLengthArray<Type>>::value), \
              QMetaType::fromType<decltype(obj)::value_type>().name())
@@ -927,10 +926,6 @@ void tst_QVarLengthArray::cpp17ctad()
     CHECK(QString, QStringLiteral("one"), QStringLiteral("two"), QStringLiteral("three"));
 #undef QVERIFY_IS_VLA_OF
 #undef CHECK
-#else
-    QSKIP("This test requires C++17 Constructor Template Argument Deduction support enabled in the compiler.");
-#endif
-
 }
 
 void tst_QVarLengthArray::first()